Question

Calculate So values for the following reactions by using tabulated So values from Appendix C. (a) N2O4(g) 2 NO2(g) So = J/K (b) 2 PCl3(g) + O2(g) 2 POCl3(g) So = J/K (c) 2 NOCl(g) Æ 2 NO(g) + Cl2(g) So = J/K (d) SO2(g) + 1/2 O2(g) SO3(g) So = J/K

Answer 1

So(rxn)=∑So (products)-∑So(reactants)

(a) N2O4(g)↔ 2 NO2(g) So = J/K

So(N2O4)=304.2 J/K.mol

So(NO2)=240.0J/K.mol

So (rxn)=(2*240-304.2) =175.8 J/K

So =175.8 J/K

(b) 2 PCl3(g) + O2(g) →2 POCl3(g)

So(PCL3)=311.7 j/k.mol

So(O2)=205.0 J/K.mol

So(POCl3)=222.4 J/K.mol

So(rxn)=2*222.4-[2*311.7+205.0]=444.8-828.4=-383.6 J/K

S0=-383.6 J/K

c) (c) 2 NOCl(g) ↔ 2 NO(g) + Cl2(g) So = J/K

So(NOCl)=261.68 J./K.mol

So(NO)=210.7 J/K.mol

So(Cl2)=223.0J/K.mol

So=[2*210.7+223]-261.68=382.72J/K(answer)

d) SO2(g) + 1/2 O2(g) ↔SO3(g)

So(SO2)=248.1J/K.mol

S0(O2)=205.0J/K.mol

So(SO3)=256.7J/K.mol

So(rxn)=256.7-[1/2*205+248.1]=-93.9J/K